Systems and Methods for Selective Electrical Isolation of Downhole Tools

ABSTRACT

Systems and methods for electrically isolating selected ones of a set of downhole tools that are connected to a common electrical cable. In one embodiment, a system includes surface equipment, a plurality of downhole tools and a common electrical cable. The downhole tools are connected to the cable by coupling switches. Each switch has a closed position in which the downhole tool is electrically coupled to the cable and an open position in which the downhole tool is electrically decoupled from the cable. The coupling switches are remotely actuated by placing an actuating device in proximity to the switches, thereby alternately coupling the corresponding downhole tools to the common cable or isolating the tools from the cable.

BACKGROUND

1. Field of the Invention

The invention relates generally to oil production, and more particularly to systems and methods for selectively coupling or decoupling individual downhole tools from a common electrical line connects the downhole tools to equipment at the surface of a well.

2. Related Art

Petroleum drilling and production operations typically involve the collection and processing of large amounts of data and the adjustment of production equipment based on the processed data. Various different tools may be installed in wells to collect the necessary information and to control well operations. For instance, gauges may be installed downhole to sense well conditions such as temperature, pressure, flow rate, etc. Control devices such as valves and packers may be installed downhole to regulate the production of oil from the wells.

Often, multiple downhole tools are connected to a single electrical cable that extends from the surface of the well, through the wellbore to each of the tools. There may, for instance, be 8-16 tools connected to a single cable. Normally, when the downhole tools are deployed in the well, the installation is considered to be permanent, and the tools are expected to remain in place for the life of the well, which may be 5-10 years or more.

One of the problems that may arise when multiple downhole tools are connected to a single cable is that the failure of one tool may adversely affect the other tools. For instance, if one of the downhole tools experiences a short circuit, the entire cable may be shorted as well, preventing the use of the remainder of the tools that are connected to the cable. Other problems (e.g., current leaks, noise caused by one of the tools, etc.) may not cause a complete failure of the system, but may complicate or reduce the utility of other tools connected to the cable.

Current protections against these types of failures or malfunctions are limited. Downhole tools may include fuses that are intended to blow out when a short circuit occurs, thereby decoupling the tools from the common electrical cable, but they are not always effective. In some cases, the fuses do not completely break the connection to the electrical cable. In other cases, the malfunction may simply not cause a high enough current to destroy the fuse. In either event, the tool remains coupled to the cable rather than being electrically isolated.

It may also be possible to provide an electrical cable for each of the downhole tools so that the malfunction or failure of one tool does not affect the others. This, however, is an impractical solution, as each cable may have to be tens of thousands of feet long and may cost tens or even hundreds of thousands of dollars. It would therefore be desirable to provide some mechanism for preventing the failure or malfunction of one of the downhole tools from affecting the ability to make use of the other tools connected to the same cable.

SUMMARY OF THE INVENTION

This disclosure is directed to systems and methods for electrically isolating selected ones of a set of downhole tools that are connected to a common electrical cable that solve one or more of the problems discussed above. In one particular embodiment, a system for producing fluids from a well includes surface equipment, a plurality of downhole tools and a cable coupled between the surface equipment and the downhole tools. At least one of the downhole tools is connected to the cable by a coupling switch. The switch has a closed position in which the downhole tool is electrically coupled to the cable and an open position in which the downhole tool is electrically decoupled from the cable. The downhole tools may include fuses in addition to the coupling switches. The switch is configured to be remotely actuated to move between the open and closed positions while the downhole tool is deployed in the wellbore. The downhole tool may be selectively coupled to or decoupled from the cable independently of other ones of the plurality of downhole tools, or an entire string of tools may be coupled to or decoupled from the cable as a group. The downhole tools may include sensors, measurement devices, control devices or other types of tools. The coupling switches may be actuated by an actuating device that is external to the tools, but is positioned in close proximity to the tools to actuate the corresponding coupling switches. The actuating device may be an electromagnet, a heating element, or some other type of device, depending upon the requirements of the coupling switches.

An alternative embodiment comprises a downhole tool. The downhole tool has one or more electrical components that are configured to be coupled to a conductor external to the downhole tool to receive power and/or communicate data. A coupling connects the downhole tool to the external conductor. A switch is connected between the electronic components and the electrical coupling. When the switch is in a closed position, the electronic components are electrically connected through the coupling to the external conductor. When the switch is in an open position, the electronic components are electrically isolated from the external conductor. The switch is configured to be actuated by an actuating device that is external to the downhole tool. The downhole tool may include sensors, measurement devices, control devices or other types of functional components. The downhole tool may include a fuse configured to isolate the electronic components from the external conductor.

Another alternative embodiment comprises a method. The method includes deploying downhole tools into the wellbore of a well, where each of the plurality of downhole tools is connected to a common cable via a corresponding switch. When it is desired to connect one of the downhole tools to the common cable or isolate one of the tools from the common cable, an actuating device is positioned in close proximity to the targeted downhole tool. The switch coupled between the downhole tool and the common cable is then actuated by the actuating device, moving the switch between a closed position in which the downhole tool is electrically coupled to the cable and an open position in which the downhole tool is electrically isolated from the cable. The downhole tool may be selectively coupled to or decoupled from the cable independently of other ones of the plurality of downhole tools, or an entire string of tools may be coupled to or decoupled from the cable as a group. The method may be performed in response to detecting a malfunction associated with the downhole tool.

Numerous other embodiments are also possible.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention may become apparent upon reading the following detailed description and upon reference to the accompanying drawings.

FIG. 1 is a diagram illustrating an exemplary well system in accordance with one embodiment.

FIG. 2 is a functional block diagram illustrating the structure of a downhole tool in accordance with one embodiment.

FIG. 3 is a diagram illustrating the manner in which coupling switches are actuated by an actuating device in one embodiment.

FIG. 4 is a flow diagram illustrating a method for isolating a downhole tool from a common electrical line in accordance with one embodiment.

While the invention is subject to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and the accompanying detailed description. It should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular embodiment which is described. This disclosure is instead intended to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

One or more embodiments of the invention are described below. It should be noted that these and any other embodiments described below are exemplary and are intended to be illustrative of the invention rather than limiting.

The present invention includes systems and methods for electrically isolating selected ones of a set of downhole tools that are connected to a common electrical cable. The downhole tools are connected to the cable by switches that can be remotely actuated to alternately couple the tools to the cable or decouple the tools from the cable. Selected tools can therefore be electrically isolated from the cable when the connection is not required, or when those tools interfere with the operation of other tools that are connected to the cable.

One embodiment of the invention is a system for enabling the electrical isolation of a downhole tool that malfunctions or fails so that the downhole tool does not affect the operation of other, interrelated systems. This embodiment is implemented in a system installed in a well for, e.g., the production of oil, gas or other fluids. The production system includes power and control equipment at the surface of the well, downhole tools such as gauges or control devices installed within the wellbore, and a common electrical line coupled between the surface equipment and the downhole tools.

Each of the downhole tools is connected to the common electrical line by a corresponding coupling switch. The switch can be set to either a closed position in which the corresponding downhole tool is electrically connected to the common electrical line, or an open position in which the corresponding downhole tool is electrically disconnected or isolated from the common electrical line. The coupling switch is actuated by an actuating device that is separate from and external to the downhole tool. The actuating device may, for example, use magnetic or electrical fields or mechanical means to actuate the coupling switches.

When the downhole tools are initially installed in the wellbore, the corresponding coupling switches are closed. If it is desired to isolate one of the downhole tools from the common electrical line, the actuating device is lowered into the wellbore, positioned in close proximity to the downhole tool to be isolated, and activated. The activation of the actuating device causes the coupling switch to be toggled to the open position, thereby electrically disconnecting the tool from the common electrical line. If it is desired to reconnect an isolated downhole tool to the common electrical line, the same procedure is used to toggle the corresponding coupling switch to the closed position.

The present systems and methods provide simple and reliable means to make or break connections between downhole tools and a common electrical line. This allows selective isolation of the tools and provides a number of benefits that are not available in conventional systems. For example, if a gauge fails and starts drawing all the available power (current), it could bring down an entire system. The present systems and methods allow such tools to be isolated, thereby enabling continued operation of the remainder of the tools connected to the common line. There could also be other potential benefits of downhole tool isolation, including power management, system reconfiguration, and so on.

Referring to FIG. 1, a diagram illustrating an exemplary system in accordance with one embodiment of the present invention is shown. In this embodiment, an oil production system is installed in a well. Production tubing 110 extends from wellhead 120 into the wellbore of the well. An electric submersible pump (ESP) 130 is coupled to the end of production tubing 110. ESP 130 pumps oil through production tubing 110 to the surface of the well. ESP 130 is electrically coupled to a drive system (not shown) which is positioned at the surface of the well and provides power to drive the ESP.

Several downhole tools (140-142) are also installed in the well. These tools may include various different types of devices, including both measurement devices and control devices. For instance, the downhole tools may comprise gauges or sensors to monitor temperature, pressure, vibration, flow rate or other conditions in the well. The downhole tools may also comprise such control devices as packers which seal selected portions of the wellbore annulus, and valves which control the flow of fluids in the well. Each of downhole tools 140-142 is connected to a common electrical line 150. This line may be, for example, a logging cable, an electrical wireline, a coiled tubing string equipped with an electrical conductor, or any other electrical line. At the surface of the well, a control unit 160 is connected to common electrical line 150 through a well interface unit 170. Common electrical line 150 enables the transmission of power and/or data between the surface equipment (control unit 160 and well interface unit 170) and downhole tools 140-142.

Downhole tools 140-142 are intended to be permanently installed in the well, and are expected to operate for the productive life of the well, which may be 5-10 years. Even though the tools are designed to have a high degree of reliability, there is a possibility that one or more of them may malfunction or fail. When this occurs, the malfunction or failure may not only prevent the use of the malfunctioning or failed tool, but may also affect the remainder of the tools or the surface equipment, all of which are connected to common electrical line 150. For instance, a current leak or complete short circuit in one tool may prevent the other tools from receiving sufficient power. A short circuit or a malfunction that causes noise on the common line may prevent the communication of data between the surface equipment and the other tools.

The present system therefore uses coupling switches to connect downhole tools 140-142 to common electrical line 150. The switches can be actuated to toggle them between closed and open positions which alternately couple the tools to the common line or isolate the tools from the common line. The coupling switch for each downhole tool is selectively actuated (separately and independently of the switches for the other tools), so that each tool can be selectively isolated from the common line when necessary (e.g., when the tool malfunctions and interferes with the operation of the other tools). This avoids any need to physically remove the malfunctioning tool (which is extremely costly), and enables the continued use of the properly functioning tools, which may allow more efficient operation of the well.

Referring to FIG. 2, a functional block diagram illustrating the structure of a downhole tool in accordance with one embodiment is shown. In this embodiment, downhole tool 200 includes a functional portion 210 and a coupling portion 220. Functional portion 210 includes the components necessary to performs the tasks required of the tool, such as sensing well conditions or controlling the flow of fluid through the production system. The components of functional portion 210 include electrical components 211, as well as any necessary mechanical components.

Electrical component 211 is coupled to the common electrical line 250 through coupling portion 220. Coupling portion 220 mechanically couples downhole tool 200 to line 250, and also serves to selectively couple or decouple electrical component 211 to line 250. In one embodiment, coupling portion 220 comprises a cable head that provides a mechanical connection of the tool's housing to the portion of the electrical line that gives the line its tensile strength. Coupling portion 220 incorporates a coupling switch 221 that is connected between electrical component 211 and the electrical conductor of line 250.

As noted above, coupling switch 221 has an open position and a closed position. When coupling switch 221 is closed, electrical component 211 is electrically coupled to line 250. When coupling switch 221 is open, electrical component 211 is electrically isolated from line 250. Coupling switch 221 is configured to be actuated by an actuating device external to the downhole tool. For instance, coupling switch 221 could be configured to be actuated by application of appropriate magnetic fields. The coupling switch could be an SPDT device that moves in one direction with one polarity of the activating magnetic flux and to the other direction with the opposite polarity. In this case, the actuating device would be a magnet that is positioned in close proximity to the switch. The physical configuration of coupling portion 220 is therefore designed to allow the actuating device to be positioned sufficiently close to coupling switch 221 to actuate and toggle the switch.

In one embodiment, electrical component 211 of the downhole tool includes a fuse. The fuse may be in line with the coupling switch so that the downhole tool is automatically disconnected from electrical line 250 in the event of an overcurrent condition. This fuse does not replace the coupling switch, but provides an additional level of protection in the event of a short circuit or similar failure. It should also be noted that, while the fuse may provide automatic disconnection of the downhole tool from the common electrical line, it does not enable the tool to be alternately connected to or isolated from the line (i.e., it does not allow the tool to be reconnected to the electrical line after it is disconnected.

Referring to FIG. 3, a diagram illustrating the manner in which the coupling switches are actuated by the actuating device in one embodiment is shown. In this figure, three downhole tools (341-342) are depicted. Each of downhole tools 340-342 is connected to a common electrical line 350. Downhole tools 340-342 and line 350 are installed in the annulus of the wellbore between the production tubing and the wall or casing of the wellbore. Electrical line 350 extends through wellhead 330 to well interface unit 360, which is connected to control unit 370.

Actuation device 310 is connected to a line that allows it to be lowered into the well through the production tubing. If actuation device 310 requires no activation (e.g., if it is a permanent magnet), the line only needs to support the device. If actuation device 310 requires activation (e.g., if it is an electromagnet), the line will have a structural component which provides support for the device, as well as an electrical component that allows the device to be activated or otherwise controlled.

When it is desired to either isolate one of the downhole tools from line 350 or couple the tool to line 350, actuation device 310 is lowered through the production tubing into a position in which it is in close proximity to the targeted tool. If actuation device 310 is a type that requires no activation, the proximity of the device to the targeted tool will actuate the coupling switch and cause it to toggle from the current position to the other position (i.e., from the closed position to the open position, or from the open position to the closed position). If actuation device 310 requires activation, it is activated after being positioned in proximity to the targeted tool, thereby causing the tool's coupling switch to toggle and either couple the tool to the common electrical line or electrically isolate the tool from the common line.

For the purposes of this disclosure, “close proximity” to the targeted tool should be construed to mean that the actuation device is close enough to the targeted downhole tool to cause the tool's coupling switch to be actuated and toggled from one position to the other. In the embodiment described above, the coupling switch is preferably positioned adjacent to the production tubing in order to facilitate its actuation by the actuating device. In other embodiments, the actuating device may be positioned external to the production tubing, so it may be preferable to position the coupling switch away from the production tubing.

It may be beneficial to employ an actuation device of a type that requires activation in order to provide improved control of the actuation process. Exemplary devices may include electromagnets or devices that selectively generate electric fields. While inactivated, the device can be moved past non-targeted downhole tools without inadvertently actuating the coupling switches of these tools. Then, when the actuation device is properly positioned, it can be activated to cause actuation of the targeted tool. If an actuation device that does not require activation is used, it may be desirable to implement the actuation of the switches in a manner that requires the actuation device to be in proximity to a switch for some predetermined minimum amount of time in order to actuate the switch. This would prevent the switches of non-targeted tools from being actuated when the actuating device passes these tools in the wellbore. Alternatively, the actuating device could be required to be properly aligned with a targeted tool before the tool's switch could be actuated.

Referring to FIG. 4, a flow diagram illustrating a method in accordance with one embodiment is shown. The method includes positioning multiple downhole tools in a wellbore, where each of the tools is connected to a common electrical line (410). It is then determined that one of the downhole tools should be disconnected (420). This determination may be based on various considerations, such as a short circuit or other malfunction in one of the tools that affects the other tools, a malfunction that prevents the tool from operating as intended (but does not affect the other tools), completion of the tool's function (e.g., an electrically set packer that has already been set), and so on. Once it has been determined that one of the downhole tools (the targeted tool) should be isolated from the common line, an actuating device is lowered into the wellbore and positioned in close proximity to the targeted tool (430). The coupling switch of the targeted tool is then actuated by the actuating device (440) to toggle the switch from the closed (connected) position to the open (isolated) position. A similar procedure can be used to identify and reconnect selected downhole tools to the common electrical line.

The embodiments described above are exemplary, and many variations of the features described above may be implemented in alternative embodiments. For example, while the foregoing embodiments utilize magnetically actuated coupling switches, an alternative embodiment could use a heat-actuated switch that employs a shape memory alloy to change from one switch position to another. The actuating device in such an embodiment would be a heating element.

In the embodiments described above, multiple downhole tools are coupled to a single, common electrical line. In alternative embodiments, there may be a single downhole tool coupled to the line, or there may be multiple electrical lines, each of which has one or more downhole tools coupled to it. In yet another embodiment, a string of multiple downhole tools may be coupled to the electrical line by a single coupling switch.

The benefits and advantages which may be provided by the present invention have been described above with regard to specific embodiments. These benefits and advantages, and any elements or limitations that may cause them to occur or to become more pronounced are not to be construed as critical, required, or essential features of any or all of the claims. As used herein, the terms “comprises,” “comprising,” or any other variations thereof, are intended to be interpreted as non-exclusively including the elements or limitations which follow those terms. Accordingly, a system, method, or other embodiment that comprises a set of elements is not limited to only those elements, and may include other elements not expressly listed or inherent to the claimed embodiment.

While the present invention has been described with reference to particular embodiments, it should be understood that the embodiments are illustrative and that the scope of the invention is not limited to these embodiments. Many variations, modifications, additions and improvements to the embodiments described above are possible. It is contemplated that these variations, modifications, additions and improvements fall within the scope of the invention as detailed within the following claims. 

1. A system comprising: surface equipment positioned at the surface of a well; a cable coupled to the surface equipment, wherein the cable extends into a wellbore of the well; and a plurality of downhole tools, wherein at least a first one of the downhole tools is connected to the cable by a switch, wherein the switch has a closed position in which the downhole tool is electrically coupled to the cable and an open position in which the downhole tool is electrically decoupled from the cable, wherein the switch is configured to be actuated to move between the open and closed positions while the first one of the downhole tools is positioned downhole in the wellbore.
 2. The system of claim 1, wherein the first one of the downhole tools is configured to be selectively coupled to or decoupled from the cable independently of other ones of the plurality of downhole tools.
 3. The system of claim 1, wherein the first one of the downhole tools comprises a sensor.
 4. The system of claim 1, wherein the first one of the downhole tools comprises a control device.
 5. The system of claim 1, wherein the switch is configured to be actuated by a magnet which is positioned in close proximity to the switch.
 6. The system of claim 1, wherein the cable comprises a conductor which is configured to provide power to ones of the plurality of downhole tools that are coupled to the cable.
 7. The system of claim 6, wherein the cable is further configured to carry data to or from ones of the plurality of downhole tools that are coupled to the cable.
 8. The system of claim 1, wherein the cable comprises a conductor which is configured to carry data to or from ones of the plurality of downhole tools that are coupled to the cable.
 9. The system of claim 1, wherein the first one of the downhole tools further comprises a fuse connected between the downhole tool and the cable.
 10. An apparatus comprising: a downhole tool having one or more electrical components that are configured to be coupled to a conductor external to the downhole tool; a coupling configured to be coupled to the conductor external to the downhole tool; and a switch connected between the electronic components and the coupling; wherein when the switch is in a closed position the electronic components are electrically connected to the coupling, and wherein when the switch is in an open position the electronic components are electrically isolated from the coupling; and wherein the switch is configured to be actuated by an actuating device which is external to the downhole tool.
 11. The apparatus of claim 10, wherein the downhole tool comprises a sensor.
 12. The apparatus of claim 10, wherein the downhole tool comprises a control device.
 13. The apparatus of claim 10, further comprising a fuse coupled between the one or more electrical components and the switch.
 14. A method comprising: positioning a plurality of downhole tools within a wellbore of a well, wherein each of the plurality of downhole tools is connected to a common cable via a corresponding switch; positioning an actuating device in close proximity to a first one of the downhole tools; and actuating the switch coupled between the first one of the downhole tools and the common cable, thereby moving the switch between a closed position in which the downhole tool is electrically coupled to the cable and an open position in which the downhole tool is electrically isolated from the cable.
 15. The method of claim 14, wherein the switch coupled between the first one of the downhole tools and the common cable is actuated independently of switches connected to other ones of the downhole tools.
 16. The method of claim 14, wherein actuating the switch coupled between the first one of the downhole tools and the common cable comprises positioning a magnet in close proximity to the switch.
 17. The method of claim 14, further comprising detecting a malfunction associated with the first one of the downhole tools, wherein the switch coupled between the first one of the downhole tools and the common cable is actuated in response to detecting the malfunction. 